Any truth behind "multipole" technology in audio signal transmission?

Question

After reading this question about ultra-expensive audio cables, I was reminded of a product that we sold at a company I used to work for.

MIT Cables makes these "audio interfaces" which go a step beyond mere audio cables, adding little electronic circuits that are claimed to transform (for lack of a better word) the audio signal. Primarily, "Multipole" technology.

Is there any truth behind these claims whatsoever?

Edit: I'm looking for either a debunking or validation of the claims, from an electrical and audio stance.

(Related question: What's the best cable to transfer audio signal?)

Answer 1

First, let me give you a little background on myself, so you can "know the source"... I'm a Sr. Electrical Engineer working in the Professional Audio field. I design high end pro-audio equipment. You've heard my stuff, as it's been used all over. I have also designed stuff for a small "audiophile" company. I'd also call myself a Skeptic, and a practical person. My pet peeve is worthless pieces of expensive audiophile junk. That being said:

There are two ways to approach this: Does it work? and Is it worth it?

Does it work: Yes! Um, no. Well, maybe. It depends on what you define as "work". If you define "work" as "can it, in theory, make a positive difference when compared to normal speaker cable" then it does work. But if you define work as "makes a positive difference that an expensive piece of gear can measure, or that can be determined by multiple listeners in a double-blind test" then the answer is no.

Is it worth it: These things cost US $8500 and make such a small improvement that no one can really hear it (or can prove that they hear it). A good pair of practical speaker cables will cost about $30. For the $8470 price difference, what could you buy that would make more of a difference in your life/happiness? A vacation to a remote tropical island? A semester in a University? The ultimate man-cave? With these speaker cables all you get is bragging rights that you can blow lots of money. Get spinners for your car, they'll attract more attention that speaker cables. So, um, no. They aren't worth it.

Here's an interesting article about comparing expensive Monster speaker cables to a wire coat hanger. Spoiler: The coat hangers work quite well.

The ideal speaker cable is short-ish, reasonably large (but not absurdly large) gauge, and set up as a twisted pair. Nothing else really matters.

Answer 2

Ah, Multipole Articulation - of course. I think I'll for my next EE new grad job interview I'll ask him/her about Multipole Articulation and watch the confused, scared look on his/her face as he/she tries to decide whether that's a real thing or just something I made up.

For the record, it's something that's entirely made up.

So let's digress a bit and talk about your stereo setup, you, and sound in general. Sound is pressure waves traveling through the air (obviously). When I say waves I mean like a sine wave - ups, downs, periods, frequencies etc. Just about the only truly interesting thing about how people think about sound is that it doesn't 'look' like a sine wave looks - The perturbations in the don't travel 'up and down' like a sine wave looks, but instead 'back and forth' like a piston. The 'up and down' waves are called 'transverse waves' and the 'back and forth' are 'longitudinal'. Sound is a longitudinal wave. Neat.

But we don't listen to sine waves (unless you love Electronica, haha, I jest) - we listen to voices and instruments. Well, luckily because of our good friend Fourier we know that all sound is a sum of many many sine waves. Just a bunch of sine waves with different frequencies, different amplitudes and phases (but also note well: we can't hear phase unless some very particular canceling out is happening - like with noise canceling headphones). So to have great reproduction of sound in a mathematical and engineering sense we need immaculate reproduction of sine waves. The measure of how well a sine wave is reproduced is called total harmonic distortion. If a sine wave is distorted it... looks funny. Odd edges, flat tops, etc. This introduces extra sine waves that weren't there originally and produces a sound that isn't the sound you're looking for. It is undesirable. THD (acronym for Total Harmonic Distortion) is generally considered good when it is much less than 1% (I think) across all frequencies. THD can vary for different frequencies, so watch out. The only other bad thing that can happen to your sine wave is to have its amplitude changed - and in general it only gets lower. This is called being attenuated.

So to accurately reproduce sound, don't attenuate your sine waves and don't introduce new frequencies that weren't there before. That's it - if you can accomplish this then you have the perfect stereo. What kind of sine waves are we playing with when we listen to our stereo? To answer that question we have to look at our ears and their limits.

Humans can hear in general sound within a range of frequency of 20Hz to 20KHz. Now at the low end you can certainly feel sound lower than 20Hz - if it's loud enough anyway - and some people can hear some sounds below 20Hz as well. As a side note, let no one tell you you can 'hear' 0Hz. 0Hz is nothing - at best a constant pressure on your eardrums. You might feel it but it's merely uncomfortable and not in any way enjoyable or a sound. And yes, it's also true that some people can hear sounds higher than 20KHz - especially so if they're very loud and particularly when the person is younger rather than older. Let me point out at this point that I seriously doubt the ability to hear high/low pitched sounds correlates to people who call themselves audiophiles (I'm betting the main correlation to people calling themselves audiophiles is the willingness to spend significant amounts of money on audio equipment).

So your cables connect your amplifier to the speakers - out of which you hear sound. Ignoring the rest of the stereo system, how do cables introduce harmonic distortion and attenuation? Let's find out.

Your cable is a wire. Wires are electrical devices with real electrical values. The ones we care about are resistance, inductance and capacitance. As EEs know, R's, L's and C's form the basis of filters. Filters attenuate sine waves and add phase (but remember we don't hear phase, so it doesn't matter), thus, your cable may attenuate your sine wave. Bad cable! To prevent this you generally need to lower the resistance. The capacitance and inductance of your basic wire is typically negligible so don't worry. We need a big honkin' thick cable to ensure our signal isn't attenuated. Big cable like... power cord. Yep, it can handle 15A, so it can handle speakers. Done! No attenuation! success!

Right? Maybe. There are other effects. Remember how I said there's capacitance in your cable? Yep, it exists. You know what else is basically a capacitor? An antenna. Yep, you cable will act like an antenna and pick up stray electrical signals. Those stray electrical signals will cause harmonic distortion in your sine waves. That's bad. How can we stop this? Actually it often doesn't matter if we stop it. Antennas operate with electromagnetic waves which follow the equation speed of light = frequency * wavelength. The wavelengths an antenna picks up are related to the length. From this site I can tell that to pick up 20KHz noise, the length of my cable would have to be about 12,000ft long. It gets worse if you want to pick up noise with a lower frequency. So you're not going to pick up anything harmful with that 20ft cable.

But let's say you want to get rid of it anyway. Fine. Get shielded cable. Shielded cable has a wire mesh around the conductor. The mesh gets grounded at some point and makes it hard for stray EM fields to work their way into your cable. This is how very expensive, highly engineered cables for very important applications are engineered, so it's overkill for a stereo setup, but hey, whatever. You can still do this fairly cheap even if you go overboard and shield each conductor. Still not made of gold, still not expensive, still no buzzwords.

So what are these cables doing with all the talk about Articulated Multipole business? What they're saying is that they will sell you three different cables, each tuned to a different frequency range. When you tune something you set the frequency response in a specific range. Since the cable is passive all it can do is attenuate the signal. So they're selling you a cable that attenuates certain sine waves. Isn't the goal to get all the sine waves through the cable without doing that kind of thing to them? Yes! I thought so anyhow. The frequency response of your basic wire is flat up to 20KHz - it doesn't attenuate anything, it just passes everything without interference. Isn't that the desirable thing?

Not for the people who want to sell you things.

I mean, it was bad enough that you can buy a lamp cord that does the job of their premium cables, but hey, they got some people to buy a set anyhow. If only they could figure out a way to get people to buy more cables to do the same thing. So they convince you that certain cables work better for certain frequency ranges. Then instead of buying one ALL-PASS cable (ie, lamp cord) you'll buy THREE PREMIUM TUNED CABLES: one high-pass cable, one mid-pass and one low-pass. Only $3995 each! Your ears will thank you!

But wait, doesn't it matter what the cable is made of? No, material mainly affects resistance. So as long as your resistance is okay it doesn't matter why. Gold? Sure, but copper is also very acceptable. Don't waste your money - measure the resistance.

Wait! Don't I need to be concerned about the poles designed into my cable? No! Poles mean filters, filters mean ACTIVE components - op amps, power supplies, etc. Are those in your cable? No! There's no room! A cable is entirely passive and shouldn't include any filtering. Filtering should be performed either in software or hardware in your amplifier. Your cable is the wrong place to be doing it.

I'll reiterate for everyone: You want a big fat dumb cable - as fat and big and dumb as possible. Luckily for you this also means cheap! Buy lamp cord at Radio Shack.

The problem with 'audiophiles' and the raft of premium audio equipment is that they're not trying to accurately reproduce sine waves. They talk about sounds being 'warm', 'bright', 'muddied' or 'veiled'. They want bright sounds and such. This means they want harmonic distortion and attenuation. After all, they buy equalizers - an instrument whose only purpose is to modify the frequency response of their entire stereo system - because they don't want their music to sound like it was recorded but instead how they like it. And since you can't measure preference, audiophile companies can sell them anything by promising various adjectives.

That's what's going on here. Snake oil pure and simple.

Answer 3

This is hogwash, and belongs in the same (fairy) realm as oxygen free copper cables (OFC, strange that I haven't seen questions about this). What you do is impression management: you tell a story which the average user doesn't understand but accepts because it sounds scientific. The hole in the theory here is that this capacitance/inductance matching occurs for just 1 frequency, while it should work for for (at least a subband of) the audio range.

The wavelength of audio signals is (for 100kHz) 3000m. Transmission line effects show as a rule of thumb from 1/10 this distance, or 300m. Below this length the important parameter is resistance. As low as possible. That's it.

In double-blind listening tests for OFC test persons can't tell any difference in sound quality. I'm sure the results for these tests on the "Multipole" cables would be the same.

Answer 4

Does it have some truth? Eh, well maybe. It is true that audio will sound different based off of the response of the channel that the signal travels through. However, I doubt that the effective inductances and capacitances that the wires have are truly noticeable to the human ear (if even seen by scopes).

It could be that they have actually placed some passive filters on the ends of the cable in order to produce a better sound. But, if you are willing to pay for higher quality cables, you probably have already paid for higher quality electronics. More then likely the electronics you are using already have methods to tune the response (EQ), this will have more of an effect then the cables can have.

Answer 5

Here is what I suggest. If you want to see how much a cable might make, see if you can borrow a set and listen to YOUR system with the content you listen to and see if YOU hear a difference. But remember, YOU can only decide if YOU hear a difference in that specific scenario. To do one listening test or to read someone else's and then make make generalizations is about the DUMBEST thing to make.

Bob Ludwig uses Transparent Cables at his mastering studio and he says he hears a difference. SkyWalker Sound uses MIT Cables in their studio and they also have custom boxes made for their microphone cables. THEY claim they hear a difference and in both cases, an improvement.

These are TWO good examples of well respected people/recording studios that I would look up to, not some person that can't afford high end cables projecting their negative bias because of some rigged blind test. Blind tests can be rigged to have whatever outcome you are looking for. Heck, even Bose would make special CDs to be used in Bose stores that were tailored to make Bose speakers sound better as they were mastered to be listened to on Bose speakers, so the customer would think that Bose are better speakers. Ooops.. Don't believe all tests that someone else did.

Do your own listening tests and don't make jealous statements that something is a rip off just because YOU can't afford it. To some people, it's worth the money to some it isn't. At least do a FAIR comparison. Take some cables home and see for yourself. You might be surprised, but spend time listening rather than talking about what you DON'T know.

Also, read the white papers at MIT. It takes a while to get through what they've done, but there is some validity to it.